<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>太极阵伪元素</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        #box {
            width: 400px;
            height: 400px;
            margin: 100px auto;
            border: 1px solid #ccc;
        }

        .box1 {
            width: 200px;
            height: 100px;
            background: #fff;
            border-radius: 50%;
            position: relative;
            margin: 100px auto;
            border: 3px solid #000;
            border-bottom: 100px solid black;
            animation: round 4s infinite linear;
            -webkit-animation: round 4s infinite linear;
        }
        @-webkit-keyframes round {
            from {
                transform: rotate(0deg)
            }
            to {
                transform: rotate(360deg)
            }
        }
        .box1:before{
            content: '';/*必须使用content插入内容*/
            position: absolute;
            width: 20px;
            height: 20px;
            top: 50%;
            border: 40px solid #000;
            border-radius: 50%;
            background: #fff;
            left: 0;
        }
        .box1:after{
            content: '';
            position: absolute;
            width: 20px;
            height: 20px;
            top: 50%;
            right: 0;
            border: 40px solid #fff;
            border-radius: 50%;
            background: #000;
            background:#000;
            border:40px solid #fff;
            border-radius: 50%;
        }
    </style>

</head>

<body>
<h1 style="text-align: center;">太极阵</h1>
<div id="box">
    <div class="box1">
    </div>
</div>
</body>
</html>